2.4.- Bioreactor and operational conditions
Bioreactor cell cultures were run in a 2-L Biostat Bplus (Sartorius
Stedim Biotech). The bioreactor was equipped with the necessary probes
to maintain the desired culture conditions regarding pH,
pO2 and temperature, stirred with two marine impellers
at 60 rpm. Dissolved oxygen (DO) concentration was measured with an
optical probe (VisiFerm DO, Hamilton). DO was set at 40% of saturation
with a constant aeration inflow of 0.20 L/min, with variable composition
controlled by a gas mix air/oxygen station. pH was measured with a
standard electrode (EASYFERM PLUS, Hamilton) and maintained at 7.1
through addition of NaOH 0.5 M solution when buffer capacity was not
enough to compensate culture acidification. CO2 inlet
gas enrichment was fixed at 5% during the entire culture. Temperature
was set at 37 ÂșC.